Pressure vessel and recyclable filter cartridge

ABSTRACT

A filter assembly is described that includes a substantially recyclable filter cartridge inside a pressure vessel. The invented filter cartridge comprises substantially non-pressure bearing walls, except for a pressure-bearing neck or cap with neck that is adapted to withstand high pressures preferably in the range of at least 200 psi, and more preferably at least 475 psi from the inside. The walls of the filter cartridge that are incapable of withstanding significant internal pressure are surrounded on the outside by a pressure vessel. The invented cartridge need not seal to the pressure vessel, because the cartridge neck protrudes outside of the pressure vessel to seal directly to a filter head. The cartridge preferably includes a quick-disassembly mechanism for allowing quick and non-destructive access to the internal components and media of the cartridge.

DESCRIPTION

[0001] This application is a continuation-in-part of and claims priorityof prior application Ser. No. 10/110,605, entitled “Recyclable FilterCartridge and Pressure Vessel” issued on Jun. 10, 2003 as U.S. Pat. No.6,576,129, and provisional application No. 60/159,018, filed on Oct. 12,1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention generally relates to filter cartridges forwater or beverages, such as those used in water, ice-water, soda popmachines, or other beverage dispensers. Specifically, the invention is afilter assembly, for cooperation with a filter head/manifold, thatincludes a filter cartridge substantially comprising recyclablecomponents. More specifically, the invention relates to a filterassembly that allows all or substantially all of the surfaces thatcontact liquid to be periodically removed and recycled, thereby reducingthe chance of contamination from long-term use of the surfaces. Thefilter cartridge is substantially non-pressure bearing, except for theneck of the filter cartridge that extends to form a liquid seal with thehead/manifold or optionally except for the cap of the filter cartridgeincluding the neck. A pressure vessel substantially surrounds the filtercartridge for holding and supporting the walls of the filter cartridgeunder liquid pressure, but the pressure vessel does not necessarilyliquid-seal to the filter cartridge or the filter head/manifold.

[0004] 2. Related Art

[0005] Many filter systems for water or other liquid filtration comprisea filter that cooperates with a “filter head,” which term hereinincludes a fluid manifold, valve head, or other connection device thatdirects fluid to and from the filter. The filter typically seals to aninternal surface of the filter head so that the liquid entering thefilter head flows into the filter, through the filter, then out of thefilter to an outlet port in the filter head. In the United States andCanada, water filters are typically required to contain and withstandpressures of about 500 psi without rupturing. In the United States,water systems typically operate in the range of 40-125 psi, and NSF(National Sanitation Foundation) approval ratings typically require awater filter to withstand 4 times the claimed maximum operatingpressure, or typically 500 psi. In Canada, safety factors require thatwater filters withstand about 508 psi for one minute. In Europe, somesafety preferences dictate a burst pressure of no less than 475 psi.

[0006] In one general type of filter system, a disposable pressurevessel connects directly to a filter head. In such a system, when thefilter media inside the pressure vessel is spent, the entire pressurevessel must be discarded, including the media contained therein.Disposable pressure vessels are not easily recyclable as there are noeasy means to disassemble the pressure vessel. The disposable pressurevessel outer wall is entirely pressure-bearing, that is, it may safelywithstand the liquid pressure of the particular system with a largesafety margin. Therefore, disposable pressure vessels are more costly toreplace because they use more plastic or more expensive materials suchas aluminum. Use of disposable pressure vessels is, therefore, costly interms of filter expense and environmental impact.

[0007] In alternative filter systems, a disposable filter cartridge maybe supplied inside a pressure-bearing housing that connects to thefilter head. In such a system, the pressure-bearing housing typicallyseals to the head using o-rings or other seals and surfaces that arecontacted by the liquid being filtered. When the media of the filtercartridge is spent, the filter cartridge is typically discarded andreplaced with another cartridge. The conventional filter cartridge hasfew recyclable components, and, the few recyclable components of thecartridge, such as granular carbon contained in the cartridge, are notremovable or easily accessible to a person who might want to recycle.While the filter cartridge is removed and thrown away, the thick-walledpressure vessel is reused. During use, portions of the pressure vesselcome in contact with the liquid being filtered, and, therefore, thepressure vessel may become contaminated with bacteria or other unhealthysubstances. Because the pressure vessel is continually reused, thecontaminated portions remain in use in the filter system and can furtherthe contamination problem in the filter system and in the liquid flowingthrough it.

[0008] Therefore, there is a need for an improved filter cartridge,which is substantially recyclable and which, therefore, reduces theresource and environmental created by the filter cartridge. Also, thereis a need for an economical and efficient filter cartridge that isdesigned so that every time the filter cartridge is removed forrecycling, the surfaces with the highest chance of being contaminatedare also replaced. The filter assembly of the present invention fulfillsthese needs.

SUMMARY OF THE INVENTION

[0009] The present invention comprises a filter assembly featuring asubstantially recyclable filter cartridge. The preferred cartridgeincludes substantially all components which are recyclable: a cartridgebody, cartridge cap, media, media-support and containment pads, andcenter stem/tubes. The cartridge preferably, but not necessarily,includes an invented mechanism or “latch” for disassembly of thecomponents of the filter cartridge so that the components may beseparated and sent to appropriate recycling processes. Further, thetotal amount of plastic or more expensive materials used in the filtercartridge is substantially less than in a conventional filter, resultingin an overall inexpensive and less problematic disposal problem, whichin general can be handled by recycling of the small amount of plasticused in the filter cartridge instead of by disposal and landfill.

[0010] The invented filter assembly preferably, but not necessarily,includes a pressure-bearing “pressure vessel” that substantiallysurrounds the filter cartridge except for the protruding neck of thefilter cartridge. The pressure vessel comes in close contact with thefilter cartridge to safely support and reinforce thenon-pressure-bearing portions of the filter cartridge, but does notnecessarily seal to the cartridge. The filter cartridge neck ispressure-bearing and protrudes out from the pressure vessel toliquid-seal directly to the filter head, in such a manner that theentire outer surface of the filter cartridge is dry, that is, notcontacted by liquid during filtration, and the entire outward pressureof liquid relative to the atmosphere is directed against the interiorwalls of the filter cartridge. This liquid pressure is contained insidethe filter cartridge neck without reinforcement, while the liquidpressure is contained inside the filter cartridge body by virtue of thesurrounding pressure vessel reinforcing the filter cartridge body wall.This is preferably accomplished by a thin-walled filter cartridge bodywith the neck wall or the cap including the neck wall beingsignificantly thicker than the filter cartridge body wall, which resultsin excellent pressure containment and NSF Safety Factors with amuch-reduced amount of total plastic to be recycled after use.

[0011] Objects of the present invention, therefore, include providing arecyclable filter cartridge for water and beverage filtration, hereinincluding filtering, treatment, or other processing. An object is toprovide such a recyclable filter cartridge that greatly reduces theenvironmental impact of the plastics and other materials used in thefilter cartridge, and that is easily disassembled for separation of thevarious components for proper recycling. A further object is to make thefilter cartridge recyclable while minimize the total amount of plasticthat must be dealt with in the recycling process. This minimization oftotal recycled plastic is preferably done by providing a thin filtercartridge outer wall except for the pressure-bearing neck or except forthe cap including the neck, which neck or cap including the neckconstitute a very small amount of wall area compared to the much largefilter cartridge body. Another object is to provide a filter cartridgesystem in which all or substantially all of the surfaces that liquidcontacts after leaving the filter head and prior to returning to thefilter head are removed from the system when the filter cartridge isremoved for recycling. Thus, the liquid-contact surfaces are filtercartridge surfaces rather than pressure vessel surfaces, and arereplaced each time the filter cartridge is replaced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a top perspective view of one embodiment of the inventedfilter assembly.

[0013]FIG. 2 is a top view of the filter assembly of FIG. 1.

[0014]FIG. 3 is a cross-sectional view of the filter assembly of FIGS. 1and 2, viewed along the line 3-3 in FIG. 2, with a dust cap installed.

[0015] FIGS. 4A and 4B: FIG. 4A is an enlarged detail cross-sectionalside view of the top end of the filter assembly, which is the endcircled in FIG. 3. FIG. 4B is an detail cross-section view as in FIG.4A, with the dust cap removed and with the filter cartridge connected toone embodiment of a filter head represented schematically.

[0016]FIG. 5 is an exploded side perspective view of the pressurevessel, which comprises a pressure body and pressure cap of the filterassembly of FIGS. 1-4.

[0017]FIG. 6 is an exploded side perspective view of the filtermaterials, media supports and filter pads, of FIGS. 1-4.

[0018]FIG. 7 is an exploded side perspective view of the central stem,optional liquid bypass sleeve and o-rings, of the cartridge of FIGS.1-4.

[0019]FIG. 8 is an exploded side perspective view of the cartridge body,cartridge cap including inlet tube member in the cap, sealing members,and dust cap of the embodiment of FIGS. 1-4.

[0020]FIG. 9 is a close-up perspective view of the exterior of theembodiment of a cartridge cap installed in a pressure vessel cap,according to the invention, with neck protruding through and up from anopening in the pressure vessel cap.

[0021]FIG. 10 is a perspective view of the pressure vessel cap of theembodiment of FIG. 10.

[0022]FIG. 11 is a perspective view of filter cartridge cap of FIG. 9,shown separate from the pressure vessel cap.

[0023]FIG. 12 is an exploded perspective view of the cartridge body andcartridge cap of FIGS. 3 and 8, separated to illustrate one embodimentof a tab and slot connection system for snapping the body and captogether.

[0024]FIG. 13 is a perspective view of the top end of the filtercartridge of FIGS. 3, 8, and 12, illustrating the cartridge cap snappedinto the cartridge body.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Referring to the Figures, there is shown one embodiment, but notthe only embodiment, of the invented filter assembly 20 which includesfilter cartridge 30 inside pressure vessel 22. The invented assembly 20comprises a pressure vessel 22 which is visible as substantially theexterior surface of the assembly, and which has an aperture 24 throughwhich the neck 44 of the filter cartridge 30 extends to seal directly toa filter head. The invented assembly 20 may be adapted for being securedto the filter head by several different ways, for example, the preferredbayonet mount 32 on the pressure cap 46, a threaded mount, or otherconnection means. Preferably, the invented pressure vessel mechanicallyconnects to the filter head, by such a connection means, but does notfluidly connect, that is, it does not fluidly seal, to the filter head.The filter assembly of the invention may be adapted to cooperate withvarious filter heads, by adapting the connection means and the size andshape of the neck, which preferably comprise the filter cartridge liquidinlet and outlet passages. The preferred embodiment of the filterassembly 20 shown in the drawings may cooperate with a filter head suchas the type illustrated by the systems in U.S. Pat. Nos. 4,857,189,Design 356,625, or 4,956,086 and, once the disclosure of the presentinvention is viewed, one of skill in the art will be able to construct afilter head that will operatively connect with the invented filtercartridge. In FIG. 4B, a filter cartridge according to one embodiment ofthe invention is shown attached to a schematic representation of onefilter head (FH) that might be used with the cartridge. The cartridgesconventionally built for such systems as shown in U.S. Pat. Nos.4,857,189, Design 356,625, or 4,956,086 are of the type described inRelated Art as a non-recyclable filter with its outer wall beingentirely pressure-bearing.

[0026] In the preferred embodiment, fluid flows via the filter head intothe central axial passage 134 in the filter cartridge 30 via an inletend 33 of inlet tube member 34 out the bottom of the central axialpassage, up through the filter media 36 (which may comprise one or moremedia, empty spaces, pads, supports, etc), and out of the filtercartridge 30 through a concentric annular passage 38 around the inlettube member 34. In the preferred embodiment, shown to particularadvantage in FIG. 3, there are three different media in series 136, 137,138, but other arrangements may be used. The filter cartridge mayoptionally include a liquid bypass system 35 for allowing some liquidflowing down the inlet tube member 34 to exit the central axial passage134 part way down the tube to flow directly to, for example, the top bed138 of media rather than flowing through all three beds of media. Theliquid bypass system 35 may include one or more holes of a diametersized to let a particular amount of liquid bypass the lower media, ormay be other systems. The liquid bypass system 35 design is optional andis not required for the invented apparatus or practicing the inventedfiltration methods.

[0027] The filter cartridge 30 extends up through a central opening(aperture 24) in the pressure cap 46 and seals to the filter head (notshown) at two locations, at o-ring 42′ (shown in FIGS. 3 and 8, ingroove 42) and at a small diameter o-ring 52′ (shown in FIGS. 3 and 8,in groove 52). This way, the neck provides and holds both sealsnecessary to fluidly connect the filter cartridge to the head using theconcentric, annular inlet and outlet system of the filter cartridge.That is, as the preferred embodiment is arranged, the inlet to thefilter cartridge is sealed at seal location 52 and the outlet of thefilter cartridge is sealed between o-rings 42′ and 52′.

[0028] The pressure vessel 22 comprises a pressure body 54, which is agenerally cylindrical member with a closed end and an open end, and apressure cap 46 that connects to the pressure body across its open end.The connection may be a threaded connection, as shown in the drawings,but may be other designs. The pressure body 54 preferably has axialexterior ribs 56 for strengthening the body. The pressure cap 46 has topaperture 24 in its generally radial upper wall 146, centered along thecentral longitudinal axis of the pressure vessel 22 for receiving theprotruding neck 44 to an extent that allows the filter cartridge to mateappropriately to the head with the sealing locations 42, 52 well abovethe pressure cap.

[0029] Inside the interior space of the invented pressure vessel 22 isplaced the invented filter cartridge 30. The cartridge 30 comprises acartridge body 64 with outer side wall surface 164 and a cartridge cap66 that connect preferably by a snap connection 68 but may be connectedby other means. The connection of cartridge body 64 and cartridge cap 66preferably includes an o-ring 8 or other liquid-sealing mechanism toprevent liquid from leaking out between the cartridge body and cartridgecap.

[0030] The cartridge body 64 is generally cylindrical with a closedbottom and an open top across which the cartridge cap 66 extends. Thecartridge cap 66 includes radially-outwardly-protruding tabs 65 that arespaced circumferentially around the bottom region of the cartridge cap66. The tabs 65 snap into circumferentially-spaced slots 67 near the topof the cartridge body for connecting the body and cap after thecartridge internals and media have been installed. The top end of thecartridge cap includes cylindrical neck 44 which is significantlysmaller in diameter than the largest diameter of the cap andsignificantly smaller in diameter than the diameter of the top of thefilter cartridge body. Preferably, the neck 44 has an outer diameter (atthe outer neck wall) of less than or equal to half of the diameter ofthe largest diameter of the cap, and less than or equal to half of thediameter of the diameter of the top end of the filter cartridge body.Preferably, the neck 44 has adaptation on its outer surface for holdingan o-ring at circumference groove 42.

[0031] The preferred internals and media of the filter cartridgecomprise one or more filter or treatment media 36, a top media felt pad82, media separator 182, separator felt pad 282, a central tube (“stem”84), the inlet tube member 34 connected to stem 84 and having inlet end33, and o-rings 42′, 52′, bypass tube 37, o-ring 108 sealing bypass tube37 to inlet tube member 34, and is bypass system 35 is included, o-ring108′ sealing bypass tube 37 to stem 84, and o-ring 109. If bypass system35 is excluded, the tube member 34 could be adapted to seal to stem 84.The central stem 84 lies on radially-formed ribs 86 on the interiorbottom wall of the cartridge body 64. Ribs 86 create a fluid path fromthe inside of stem 84 into media 36. The stem 84 upends from the ribs 86to extend through the interior space and through the pads, mediaseparators, and media 36 contained therein to seal with the inlet end33. The media 36 may be any single media or combination of media desiredfor liquid/beverage treatment, filtration or conditioning. Media 36 arepreferably granular activated carbon and ion exchange resin, and thismedia choice may be taken into account by one skilled in the art whenselecting the supports and pads below, between, and above the variousmedia.

[0032] Inside and coaxial with inlet tube member 34 is an optionalbypass sleeve 37 with a lower portion 37′ that connects to stem 84 andmay optionally have holes, o-rings, or other structure for providing aliquid bypass system. The structure 133 shown at the top of the sleeve37 and in the top inside view of sleeve 37 in FIGS. 12 and 13 maycooperate with the dust cap C shown in FIGS. 3, 4, and 8. Dust cap C maybe used to keep the inlet and outlet of the cartridge clean, and,optionally, may cooperate with structure 133 to allow adjustment of thesleeve 37 to adjust the liquid bypass by rotating the sleeve. As statedabove, the liquid bypass is optional and may be closed, blocked off oreliminated.

[0033] From a fluid flow point of view, the fluid enters the inlet end33 (and through the interior of sleeve 37) and flows down into the stem84, and out through radial ribs 86 in the bottom of cartridge body 64 tothe media 136. As mentioned above, a liquid bypass system 35 mayoptionally be incorporated to allow a portion of the liquid to flow onlythrough a portion of the media zones. From the media 136, the liquidflows generally axially upwards through the other media 36, supports andpads, through apertures in the inlet tube base and into the annularspace 38 between the inside surface of the cartridge cap 66 and theoutside surface of the inlet end 33. Annular space 38 may include ribs71 running axially in the annular space 38 to stabilize the inlet end 33relative to the cartridge cap.

[0034] As can be seen to best advantage in FIG. 3, the cartridge 30 fitsclosely inside the pressure vessel 22, and the pressure vessel 22 actsas a reinforcing shell around substantially all of the cartridge 30.Unlike many conventional filter cartridges, however, the cartridge 30,particularly neck 44, of the present invention extends at its top endout of the pressure vessel to seal directly to the filter head. Thepressure vessel and filter cartridge, therefore, need not liquid seal toeach other, although the inventor envisions adequate embodiments thatwould include sealing between the filter cartridge and pressure vessel.In the preferred embodiment, liquid does not flow or reach between thepressure vessel cap and the cartridge cap, that is, there need be noliquid seal in the general location L where the two caps 46, 66 contactor come near to each other near the aperture 24. Also, the cartridgebody 64 need not seal to the inner surface of the pressure vessel body54, but should be closely adjacent.

[0035] The various components of the cartridge 30 are preferablyrecyclable. Specifically, the cartridge body 64, cap 66, stem 84, spacer86 are preferably recyclable polyethylene, polypropylene, oracrylonitrile butadiene styrene (ABS) for example. The various media 36are preferably recyclable carbon, resin, or other material. The internalpads and medai supports are preferably made of recyclable materials suchas polyurethane or polypropylene. The O-rings may not be recyclable, butthese are preferably the only components that are not, and they are verysmall, easily removed and should be removed and discarded to preventback-contamination with any bacteria or pathogens that might be presenton them or on the o-ring lubricating oil.

[0036] The absolute wall thickness of the neck 44 is important as it iscritical to the filter cartridge and the filter assembly, in general,meeting safety requirements for withstanding water pressure of thesystem to which they are connected. For example, to withstand a 500 psitest, the polypropylene neck wall thickness T preferably greater than orequal to 0.125 inch in thickness, while the filter cartridge body wallpreferably only about 0.060 inches (typically in the range of0.050-0.070) in thickness. Therefore, the body wall typically is lessthan about half the thickness of the neck thickness. Other thicknessesmay apply for various materials and pressure requirements. As shown inFIGS. 3 and 4A, the neck preferably may be thick-walled from the top 144of the neck, all the way through the aperture 24 and for a slightdistance down into the pressure vessel to neck bottom 244, to preventrupturing of the neck in the vicinity of the aperture 24, as this is theneck wall area wherein the thick pressure-bearing feature is especiallyrequired. Optionally, the cap may be thick-walled further down into thepressure vessel or the entire cap may be thick-walled, for ease ofmanufacture, for example. Still, with either option (of substantiallyonly the neck of the cap being thick-walled, or all/substantially all ofthe cap being thick-walled), the filter cartridge body is thin-walledand non-pressure bearing, as the body is the largest element of thefilter cartridge and is generally controlling in the economy ofmanufacture and recycling efficiency. Thus, for example, the entireplastic cap may comprise a wall of greater than or equal to 0.125 inchthickness, while the entire plastic body wall may be in the range of0.05-0.07 inches thick, for example. FIG. 4B illustrates one embodimentof a cap that is thick all along its wall, from the top of the neck toits connection to the body.

[0037] The inlet tube member 34 wall, which also extends up coaxiallywith the neck wall out of the pressure vessel, does not need to be of athickness comparable to the neck wall, because the inlet tube is notexposed to a large pressure difference as the neck wall is. The neckwall withstands the full pressure difference between the water in theneck and the outside atmosphere, while the inlet tube has water bothinside it (inlet water) and outside it (outlet water) and the pressuredifference between the two water streams is only the pressure dropthrough the filter cartridge.

[0038] Therefore, one may describe the preferred invented filtercartridge as having an exterior wall having a high strength portion anda low strength portion. In the preferred embodiment, the exterior wallis the entire outer wall of the filter cartridge including the body andcap. The high strength portion is defined as being adapted to withstandpressure of greater than or equal to 200 psi, and most preferablygreater than or equal to 475 psi, and is preferably a neck that extendsup from the center of one end of the filter cartridge, or, alternativelythe cap including the neck. The low strength portion is defined as beingadapted to withstand only minimal pressure, for example less than orequal to 50 psi, and, in order to minimize the total plastic, morepreferably less than or equal to 10 psi, and is preferably the entiretyof the outer wall of the filter cartridge except the above describedneck, or alternatively, the entire outer wall of the filter cartridgeexcept for the cap including the neck. Also, the term “pressure bearing”in this Description and Claims means positioned and capable of bearingby itself (without significant reinforcement) the pressure of the fluidin the process in which it is being used. The term “non-pressurebearing” means that a part or portion of a structure is not positionedin a place where it will be exposed to significant pressure, that is,not more than a negligible amount, and especially not more than about 50psi.

[0039] One may see from this description and the drawings, that thefilter assembly, comprising the filter cartridge and the pressurevessel, may be removed from the head and the recyclable filter cartridge30 may easily be removed from the pressure vessel by unscrewing orotherwise disconnecting the pressure cap from the pressure body. Then,the cartridge may be recycled after being disassembled as describedbelow, for example. Other mechanisms for easy opening of the filtercartridge may be used, and these are called herein “latch mechanisms” asthey allow closing of the filter cartridge after filling of thecartridge body with media, and then allow opening of the filtercartridge without excessive force or destruction of the body or capafter use. In this Description and the Claims, latch does not imply thatno cutting or removal of filter cartridge material may be done tounlatch parts of the exterior wall, but preferably only cutting orremoval of a tab or other small portion of a latch is done rather thandestruction by impact, sawing, or slicing the body. Preferably, twoparts of the low strength portion of the filter cartridge exterior wallare the parts that are “latched” and “unlatched,” at a seam orconnection 68, for example. When the preferred cartridge is removed fromthe preferred pressure vessel, the cartridge takes with it all thesurfaces and seals that have contacted liquid on the “filter assemblyside” of the process. Thus, potentially contaminated surfaces ando-rings are removed periodically rather than remaining with the reusedpressure vessel. Some contamination may reside on the “filter head side”of the process, because the filter head is not recycled or replaced, butthe total head surfaces as typically small in area, and, if the o-ringsare removed with the filter cartridge, the chances of o-ring lubricantcontamination, for example, are minimized.

[0040] In order to disassemble the cartridge 30, special adaptation ispreferably included to allow separation of the components of thecartridge 30 without crushing or cracking the cartridge. Preferably, theadaptation is such that accidental separation is unlikely, butpurposeful separation prior to recycling is easy with the correct tool.Preferably, the adaptation comprises a snap-in tab and slot system,illustrated to best advantage in FIGS. 12-13, or other separation systemfor opening the cartridge, preferably without cracking, crushing, ordrilling through the cartridge housing. The tabs 65 are typically formedintegrally with the cartridge cap 66 near its lower end. The cooperatingslots 67 near the upper edge of the cartridge body 64 receive the tabs65 in snap-fit manner, to semi-permanently connect the cap 66 to thebody 64. The outer perimeter of the lower end of the cap 66 includescut-away portions 69 directly above each tab 65 so that the tab and slotconnection may be reached by a tool. When the user of recycler wishes todisassemble the filter cartridge 30, he/she may slide a knife or sharptool down between the cap 66 and the body 64 directly above the tab andslice downward on the tab to remove enough of the tab to release thebody from the cap. This, or other types of separation, allow a person orequipment to reach inside the cartridge, to remove the internals and themedia from the cartridge for recycling of the internals and media aswell as the external cap and body components.

[0041]FIG. 4B illustrates the flow into and out of the preferred filtercartridge, and one of various filter heads (FH) that may be adapted foruse with embodiments of the invented filter cartridge.

[0042] Although this invention has been described above with referenceto particular means, materials and embodiments, it is to be understoodthat the invention is not limited to these disclosed particulars, butextends instead to all equivalents within the scope of the followingclaims.

I claim:
 1. A liquid filter cartridge for connection to a filter head,the filter cartridge comprising: a cartridge body having an exteriorwall having a high strength portion and a low strength portion; the highstrength portion being adapted to connect to and fluidly communicate toa filter head and adapted to withstand internal pressure of greater than200 psi, and the low strength portion being adapted to withstand notgreater than 50 psi and to be removable received inside a pressurevessel that does not enclose and does not support the high strengthportion; the low strength portion defining and surrounding an interiorspace containing filter media; and the exterior wall comprising a latchthat closes the exterior wall around the filter media and opens theexterior wall for removal of the filter media.
 2. A filter cartridge asin claim 1 comprising an elongated cartridge body and a cartridge cap,the cap having a protruding neck having a neck wall and fluid inletpassage and a fluid outlet passage within the neck wall, and the neckwall being the high strength portion.
 3. A filter cartridge as in claim2, wherein the neck comprises a plurality of seals adapted to seal to afilter head, including a seal on an outer surface of the neck wall. 4.The filter cartridge as in claim 3, wherein the seals of the neck arethe only means for fluid sealing the filter cartridge to the filterhead.
 5. The filter cartridge of claim 2 wherein the neck wall isgreater than or equal to 0.125 inch and the low strength portion is lessthan 0.07 inch.
 6. The filter cartridge of claim 1, wherein the exteriorwall is made of plastic.
 7. The filter cartridge of claim 1, wherein theexterior wall is separable into at least two parts and the latchreleasably connects said parts, wherein the latch comprises a tab on oneof said parts that snaps into a slot on another of said parts.
 8. Thefilter cartridge of claim 7, wherein the latch is released by cuttingthe tab off of the filter cartridge exterior wall.
 9. A filter assemblyfor connection to a filter head for receiving fluid from the filter headfor filtration, the filter assembly comprising: a recyclable filtercartridge containing media, and a pressure vessel; the filter cartridgecomprising an exterior wall having a pressure-bearing neck portionadapted to sealably connect to a filter head and a non-pressure bearingportion received inside the pressure vessel; wherein the pressure vesselcovers the non-pressure bearing portion but does not cover thepressure-bearing neck portion.
 10. A filter assembly as in claim 9,wherein the neck portion is adapted to seal to the filter head so thatfluid from the filter head does not contact the pressure vessel and doesnot contact the non-pressure bearing portion of the exterior wall.
 11. Afilter assembly as in claim 9, wherein the pressure vessel comprised apressure cap having an aperture through which the neck portion protrudesfor sealing with the filter head.
 12. A filter assembly as in claim 11,further comprising a connection system for attaching the pressure vesselto the filter head, the connection system located on the pressure vesseland not on the neck.
 13. A filter assembly as in claim 12, wherein theconnection system comprises bayonet lugs on the pressure vessel.
 14. Afilter assembly as in claim 9, wherein the pressure vessel does notfluid-seal to the filter cartridge.
 15. A pressure vessel for containinga filter cartridge having a mechanical connection to a filter headwithout any fluid connection to the filter head.
 16. A liquid filterassembly for connection to a filter head, the filter assembly comprisinga pressure vessel and a filter cartridge removably received in thepressure vessel, the filter cartridge comprising: a generallycylindrical housing surrounding an interior volume receiving filtermedia and having a central longitudinal axis and a radial dimensiontransverse to the central longitudinal axis, the housing having ahousing wall comprising an axial outer sidewall with an outer diameter,a generally radial outer bottom wall forming a cartridge bottom end, agenerally radial outer top wall forming a cartridge top end, and thehousing further having a neck upending axially from the top wall at ornear said central longitudinal axis, wherein the neck has a neck outerdiameter that is smaller than the outer diameter of said outer sidewall;wherein the neck comprises a neck wall with an outer surface, an innersurface, a neck lower end attached to the top wall, and a tube membergenerally coaxial with the neck wall and having a central axial passage,the tube member being spaced from the neck wall inner surface to createa neck annular passage between the tube member and the neck wall,wherein said central axial passage and said neck annular passage areliquid inlet and outlet passages for the filter cartridge; wherein theneck wall has a thickness adapted to withstand pressure in the neckannular passage at least 200 psi greater than pressure outside the neckwall; wherein said pressure vessel surrounds and reinforces the entirehousing except for the neck, the pressure vessel having a generallyradial upper wall with an aperture through which the neck protrudes andwherein said upper wall extends from near the outer sidewall of thehousing across the top wall of the housing generally radially to thelower end of the neck wall to cover and reinforce the entire cartridgetop end except for the neck; and wherein said pressure vessel comprisesa first portion and a second portion adapted to be detached from eachother so that the pressure vessel is openable for removing of saidfilter cartridge from the pressure vessel.
 17. The liquid filterassembly of claim 16, wherein the neck outer diameter is about half theouter sidewall outer diameter.
 18. The liquid filter assembly of claim16, wherein the neck wall has a thickness of greater than or equal to0.125 inches.
 19. The liquid filter assembly of claim 18, wherein thehousing wall has a thickness in the range of 0.05-0.70 inches.
 20. Theliquid filter assembly of claim 18, wherein the housing wall has athickness of less than about half of the neck wall thickness.
 21. Theliquid filter assembly of claim 18, wherein the neck wall ispolypropylene and wherein the housing wall is polypropylene and has athickness of about half of the neck wall thickness.
 22. The liquidfilter assembly of claim 16, wherein the housing wall has a thicknessadapted to withstand a pressure inside the housing wall of no more than10 psi greater than outside the housing wall.
 23. The liquid filterassembly of claim 16, wherein said filter housing wall is plastic andcomprises a latch that is unlatchable so that the filter housing wall isopenable for emptying of media out from the filter cartridge andrecycling of the plastic of the housing wall.
 24. The liquid filterassembly of claim 23, wherein said housing wall comprises a body portionand a cap portion and said latch comprises a tab on said body portionextending into said cap portion, and wherein the latch is unlatchable bycutting the tab off of the body.
 25. The liquid filter assembly of claim16, wherein said neck wall comprises a sealing member for sealing to afluid passage of a filter head, and said tube member comprises a sealingmember for sealing to a fluid passage of the filter head, and whereinthe filter cartridge comprises no means for liquid-sealing the filtercartridge to a filter head other than said sealing member of the neckwall and said sealing member of the tube member.
 26. The liquid filterassembly of claim 16, wherein said pressure vessel does not fluid-sealto the filter cartridge.
 27. A filter system comprising a liquid filterassembly and a filter head with inlet and outlet fluid passage, thefilter assembly comprising a pressure vessel and a filter cartridgeremovably received in the pressure vessel, the filter cartridgecomprising: a generally cylindrical housing surrounding an interiorvolume receiving filter media and having a central longitudinal axis anda radial dimension transverse to the central longitudinal axis, thehousing having a housing wall comprising an axial outer sidewall with anouter diameter, a generally radial outer bottom wall forming a cartridgebottom end, a generally radial outer top wall forming a cartridge topend, and the housing further having a neck upending axially from the topwall at or near said central longitudinal axis, wherein the neck has aneck outer diameter that is smaller than the outer diameter of saidouter sidewall; wherein the neck comprises a neck wall with an outersurface, an inner surface, a neck lower end attached to the top wall, aliquid seal member on the neck wall, and a tube member generally coaxialwith the neck wall and having an central axial passage, the tube memberbeing spaced from the neck wall inner surface to create a neck annularpassage between the tube member and the neck wall and the tube memberhaving a liquid seal member, wherein the central axial passage and theneck annular passage are liquid inlet passage and liquid outlet passagesfor the filter cartridge; wherein the neck wall has a thickness adaptedto withstand pressure in the neck annular passage at least 475 psigreater than pressure outside the neck wall; wherein the pressure vesselsurrounds and reinforces the entire housing except for the neck, whereinthe pressure vessel has a generally radial upper wall with an aperturethrough which the neck protrudes and wherein said upper wall extendsfrom near the outer sidewall of the housing generally radially acrossthe top wall of the housing to the lower end of the neck wall to coverand reinforce the entire cartridge top end except for the neck; andwherein the pressure vessel is mechanically connected to the filter headand wherein the tube member liquid seal member and the neck wall liquidseal member seal to said inlet and outlet filter head passages so thatliquid flows from the filter head in and out of the filter cartridge viathe central axial passage and the neck annular passage and does notcontact any surfaces of the filter head except said inlet and outletfilter head passages, does not contact the pressure vessel, and does notcontact the neck wall outer surface below said liquid seal member of theneck wall, for minimizing surface area of filter head and externalsurface area of the filter cartridge exposed to the liquid during use.28. The liquid filter assembly of claim 27, wherein the neck outerdiameter is about half the outer sidewall outer diameter.
 29. The filtersystem of claim 27, wherein the neck wall has a thickness of greaterthan or equal to 0.125 inches.
 30. The filter system of claim 29,wherein the housing wall has a thickness in the range of 0.05-0.70inches.
 31. The filter system of claim 29, wherein the housing wall hasa thickness of less than about half of the neck wall thickness.
 32. Thefilter system of claim 29, wherein the neck wall is polypropylene andwherein the housing wall is polypropylene and has a thickness of abouthalf of the neck wall thickness.
 33. The filter system of claim 27,wherein the housing wall has a thickness adapted to withstand a pressureinside the housing wall of no more than 10 psi greater than outside thehousing wall.
 34. The filter system of claim 27, wherein said neck wallcomprises a sealing member for sealing to a fluid passage of a filterhead, and said tube member comprises a sealing member for sealing to afluid passage of the filter head, and wherein the filter cartridgecomprises no means for liquid-sealing the filter cartridge to a filterhead other than said sealing member of the neck wall and said sealingmember of the tube member.
 35. The filter system of claim 27, whereinsaid pressure vessel does not fluid-seal to the filter cartridge anddoes not fluid-seal to the filter head.